New material could provide massive boost to solar cell efficiency

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A group of scientists working with the University of Utah believe they’ve discovered a method of substantially boosting solar cell efficiencies, in a breakhrough that could significantly reduce the total cost per watt — if it can be successfully commercialized.

Traditionally, solar cell technology has struggled to overcome a significant efficiency problem. The type of substrate used dictates how much energy can be absorbed from sunlight — but each type of substrate (silicon, gallium arsenide, indium gallium arsenide, and many others) corresponds to capturing a particular wavelength of energy. Cheap solar cells built on inexpensive silicon have a maximum theoretical efficiency of 34% and a practical (real-world) efficiency of around 22%. Multijunction cells that use multiple substrates to capture a larger section of the sun’s spectrum can reach up to 87% efficiency in theory, but are currently limited to 43% in practice. What’s more, these types of multijunction cells are extremely expensive — wiring and laying out precise structures is far more difficult than a simple thin film silicon cell.

We have a vast array of cells, but all of the inexpensive, common designs are low-efficiency. Image courtesy of Wikipedia

What the team has developed is a polychromat layer that separates and sorts incoming light, redirecting it to strike particular layers in a multijunction cell. The test device used two layers — indium gallium phosphide (for visible light) and gallium arsenide for infrared light. According to the research team, “When the University of Utah polychromat was added, the power efficiency increased by 16 percent.” The team also ran simulations of a polychromat layer with up to eight different absorbtion layers and claim that it could yield an efficiency increase of up to 50%, but have not actually tested the technology.

The polychromat layer sits on top and splits energy wavelengths, aiming them at the layers where they’ll be absorbed.

This is where the reporting gets a little tenuous. The University of Utah statement refers to single-junction solar panels but describes a multi-junction device. Furthermore, it states the gain as a percentage rather than “percentage points.” This implies that the sentence should be understood as a percent of a percent; if the original cell efficiency was, say, 30%, then a gain of 16% percent means that the new efficiency is 34.8% (30 percent * 1.16x). That’s still a huge gain for a polychromat layer that the researchers say could be stamped out using DVD-like technology, but it’s not quite the enormous advance it’s been depicted as.

Given that the biggest barrier to III-V multi-junction solar cell technology is manufacturing complexity and associated cost, anything that boosts cell efficiency on the front end without requiring any major changes to the manufacturing process is going to help with the long-term commercialization of the technology. Until now, most of the multijunction devices deployed go into space or are used by for military applications where cost is less of an issue and peak performance is essential. Advances like this could help make technologies cost effective for personal deployment and allow them to scale in a similar fashion to cheaper devices.

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Efficiency is nice, depending on price. But what would be REAL nice, is if you solar guys stopped making solar panels, and started making solar ROOFING panels.

The biggest problem solar panels have is not efficiency, or even cost. It’s maintenance. If you have to fix the roof, the solar panels are in the way. Taking them down, storing them, putting them back up will double the cost of a roof replacement. And will also damage some of the panels. Its one of those things that doesn’t point itself out right away. But now that you thought of it, you can see it coming from Georgia.

A solar roof will last quite a while. Painted on metal, maybe 50 years. When times up, you recycle it and put a new one on. Boom, done! And a roof is BIGGER than a panel, so lower efficiency isn’t a big problem. A 5 x 20 Meter, %10 efficient roof would peak at 10 kilowatts. A typical location with typical power rates would currently see $1600 of power annually from that inefficient system. In southern Cal, $2500.

More efficiency is better, of course. But the perfect is the enemy of the good. So, make with the roofing already! We need the cheap, clean, reliable power. And the shade.

Bill

That is already beeing done in the USA. One initiative (look away if you dont like product placement) Dow Powerhouse Solar Shingles

Kurtis Engle

That’s true, Bill. The DOW Powerhouse shingle has been available about five years now. However, one can’t seem to buy these things. There just don’t seem to be very many of them. It’s like they were thought to be a NOVELTY ITEM. And these particular shingles have only a 20 year warranty. That’s NOT the sort of roof I want to fiddle with. I want to set it, and forget it.

Luke Hill

That’s a job for different people. The people trying to make solar panels more efficient are not structural engineers.

Kurtis Engle

That might be fair.

Magnus Blomberg

“The polychromat layer sits on top and splits energy wavelengths, aiming them at the layers where they’ll be absorbed.” should be “The polychromat layer sits on top and splits energy depending on wavelengths, aiming them at the layers where they’ll be absorbed.” The wavelength is a property of the wave.

Radio/light wavelength and radio frequency are frequently miss used in the English language. People write/say radio frequency when they mean an electromagnetic wave of radio frequency/radio wavelength.

The wave is the object and the wavelength/frequency is a property of the wave.

James

Far too frequently indeed.

jerrystroud

One problem with the polychromate in solar cells…..the power source (the Sun) causes the polychromate to become less efficent in time due to fading, discoloration, etc. One thing you can always count on and that is nothing is permanent.

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